Interpretive Summary: The use of fungi to control weeds (bioherbicides) is an innovative approach to sustainable pest control. The fungus Myrothecium verrucaria (MV), isolated from the weed sicklepod also controlled kudzu and several other weeds and understanding the risks and limitations for use as a bioherbicide is being investigated. Greenhouse and field studies indicate a treaments of MV plus a surfactant caused 100% mortality to kudzu seedlings in the greenhouse, and 90 to 100% control of older kudzu plants in naturally-infested and experimental plots, respectively. Greater control of kudzu was found at 30° C, compared to 20 or 40° C. Responses of various non-target, young, woody plant species from several plant families to MV ranged from non-susceptible to moderately-susceptible, indicating the potential to use this fungus in areas of mixed vegetation. MV possess desirable traits as a bioherbicide (high efficacy and control of several weed species), but this isolate also produces mycotoxins, i.e., trichothecenes. Approaches to reduce or eliminate these mycotoxins in order to develop a safe and efficacious bioherbicide are discussed.

Technical Abstract:
Studies were conducted on a Myrothecium verrucaria (MV) isolate from sicklepod (Senna obtusifolia L.) that exhibits bioherbicidal activity against kudzu [Pueraria lobata (Willd.) Ohwi] and several other weeds. Treatments of MV plus the surfactant SilWet L-77 caused 100% mortality or control to kudzu seedlings under greenhouse conditions, and 90 to 100% control of older kudzu plants in naturally-infested and experimental kudzu plots, respectively. MV caused greater reductions of kudzu plant biomass production at 30° C, compared to 20 or 40° C in environmental chamber experiments. Responses of various non-target, young, woody plant species from several plant families to MV ranged from non-susceptible to moderately-susceptible. Bioassays of MV on seed germination and early growth of sicklepod and hemp sesbania demonstrated that hemp sesbania was more sensitive than sicklepod. Although MV possess desirable bioherbicidal traits such as high efficacy and the ability to control several species of weeds, this isolate also produces unwanted mycotoxins, i.e., trichothecenes. Data on this research is presented, as well as discussion of some future approaches to reduce or eliminate these mycotoxins in order to develop a safe and efficacious bioherbicide.